The aim of this paper is to present the main ideas that could form the core of the Post-Keynesian approach to the analysis of labour demand at both micro- and macroeconomic levels. Specifically, this paper first reviews the essential elements characterising the Post-Keynesian approach to microeconomic analysis of labour demand. To do this, the "traditional view" is first presented, associated with the concept of the firm characterised by the presence of fixed technical coefficients and capacity reserves, and then the essential features of an alternative and more innovative view are described, based on the concept of the firm that emanates from the competence-based theories of organisation. Subsequently, the core of the Post-Keynesian contributions at the macroeconomic level is presented, organising them into two sections: first, those contributions that break away from the "second classical postulate" and second, those that additionally steer away from the "first classical postulate". Finally, the paper summarizes the main ideas that could be the core of the post-Keynesian approach to the analysis of labour demand, both in micro- and macroeconomic fields.